1. Field of the Invention
The present invention relates to a spin valve device containing a chromium-rich antiferromagnetic thin film which pins a magnetoresistive ferromagnetic thin film through exchange coupling.
2. Description of the Background
Exchange-biased spin valve multilayers are a class of metallic multilayer materials which display the giant magnetoresistive (GMR) effect. Recently, spin valves have received increasing attention for application in magnetoresistive sensors, most notably in read heads for hard disk (HD) and tape magnetic storage devices, where they provide greater sensitivities as compared to read heads based on conventional anisotropic magnetoresistive materials. For a discussion of spin valve devices see J. C. S. Kools, "Exchange-Biased Spin Valves For Magnetic Storage", IEEE Transactions on Magnetics, Vol. 32, no. 4, July, 1996, p. 3165-3184, incorporated herein by reference. For a description of using spin valves and related devices for magnetic recording applications, see U.S. Pat. Nos. 5,301,079, 5,436,777 and 5,471,358.
Exchange induced unidirectional anisotropy has been observed in a variety of bilayer systems, such as Ni--Fe/Fe--Mn2!, Ni--Fe/NiO and Ni--Fe/Co--Ni--O5!, Ni--Fe/Ni--Mn6!, and Ni--Fe/.alpha.Fe.sub.2 O.sub.3 and Ni--Fe/Tb--Co7!. Fe--Mn (50/50) has a disordered fcc structure and is the most extensively studied antiferromagnetic film, followed by the oxides of Co and Ni. The equilibrium structure of FeMn is the so-called .alpha.-phase, which is bcc. Therefore, a lattice-matched underlayer is often required to stabilize the antiferromagnetic fcc phase3!. TbCo is amorphous and little work has been done on this alloy. Nearly equiatomic Ni--Mn is known to be antiferromagnetic only in the CuAu--I--type (L1.sub.0) ordered structure8!. Therefore, Ni--Mn films sputtered at ambient temperature, which are usually disordered fcc, require annealing to enhance exchange coupling6, 9!. In addition, FeMn and TbCo are known to be very sensitive to corrosion, which is unacceptable for technological applications.
Accordingly, there remains a need for spin valve devices which overcome these disadvantages.